As the basic building blocks of the micro- or nano-devices, nano-scale materials carry the information transport, storage and other important functions. The interest in the trend to reduce the dimensions of these devices in the semiconductor and information industries has given rise to a necessity for developing techniques for studying microstructure and the size effects on the mechanical strength and charge transport properties of individual functional nanostructure under external stress field and electric field. It is of great significance to the function of various units, storage density, efficiency, reliability and practical application of the devices.
Transmission electron microscopy (TEM) is a powerful tool for characterizing the micro-structures of solid state materials in the field of nano-science and nano-technology. In situ TEM experiments provide direct visualization and description of the events as they happen and give qualitative information about the structure-property-processing relationships. These knowledge are vital not only to the design and functional the nano-devices but also to the reliability and service. TEM grid is used to support the detected samples, which is usually Cu grid 3 mm in diameter with thin carbon film coatings. But at present the TEM grid is effective only for the static testing, and not for in situ manipulation and dynamic quantitative testing the properties of nano-material at the nano-scale even to atomic scale level.
Several approaches have been studied for in situ TEM manipulating, in order to quantitatively measure and image the structure-property relationships of individual nanostructure. See M. A. Hague and M. T. A. Saif, “Deformation mechanisms in free-standing nanoscale thin films—A quantitative in situ transmission electron microscope study” Proceedings of the National Academy of Sciences, Vol. 101, p. 6335, 2004; J. Y. Huang, S. Chen, S. H. Jo, Z. Wang, D. X. Han, G. Chen, M. S. Dresselhaus, and Z. F. Ren, “Atomic-Scale Imaging of Wall-by-Wall Breakdown and Concurrent Transport Measurements in Multiwall Carbon Nanotubes”, Physics review letters, Vol. 94, 236802, 2005; and Yong Zhu and Horacio D. Espinosa, “An electromechanical material testing system for in situ electron microscopy and applications”, Proceedings of the National Academy of Sciences, Vol. 102, p. 14503-14508, 2005. These methods integrated the micro-electromechanical systems (MEMS) unit with the TEM holder, thereby enabling simultaneous TEM observation and mechanical measurements, for investigating the relationship between nano-scale microstructure and interaction of individual nanostructure. But installing these devices inside the TEM holder that causes the holder can tilt a small angle and only a single axis tilting because of the narrow pole-piece gap. However, atomic-scale lattice resolution of a crystal is only achieved when a low-indexed zone axis of a crystal is precisely aligned parallel to the electron beam. This condition is difficult to fulfill in these in situ measuring systems that are subjected to mechanical manipulation influence during the experiments. Otherwise, the strain quantitation which reflects to mechanical property of nano-material calculating from the in situ high resolution TEM images present large error derived from artificial measuring process.
In recent years, accompany with development of science and technology, cantilever beam technology has been widely used in biology, physics, chemistry, materials, microelectronics and other research fields. These cantilever sensors obtained via lithography, etching and other processes on silicon-based material can be achieved high sensitivity, and the signal to noise ratio of the sensors are also very low, such as: IEEE Sensors Journal, Vol. 7, No. 1, 2007. However, it is difficult to integrate these sensors into the transmission electron microscope for real-time observation of microstructure, because of its large size, as well as the device that contains complex optical measurement systems which are applied to obtain displacement of cantilevers.